The invention relates to rocket engines and, more specifically, to the design of a combustion chamber for liquid-fuel rocket engines. The invention can be used in aircraft engine manufacturing and, to a certain extent, in heat engineering.
Known in the art is a stratified nozzle for a solid-fuel rocket engine (U.S. Pat. No. 3648461) in which the internal insulation layer on the side of fire cavity may be ablative or non-ablative. This technical solution is deficient because of the problems associated with its effective implementation in the production of regeneratively cooled chambers of liquid-fuel rocket engines (LRE).
Prior knowledge also includes the use of coatings in LRE combustion chamber envelopes, as attested by the disclosure of LRE combustion chambers in which the effect of thermal flows is minimized by protecting their walls with ceramic heat-insulating coatings (Encyclopedia xe2x80x9cCosmonauticsxe2x80x9d, chief ed. V. P. Glushko, M, 1985, p. 153).
The description of this design does not disclose the materials of coatings used with specific chambers, wherefore it is not clear how to achieve an appreciable extension of the service life of specific combustion chambers operating on oxygen-kerosene propellant components. Data, however, are provided on an LRE combustion chamber having a high temperature molybdenum insert with a protective zirconia coating.
The closest prior art of the present invention is a combustion chamber casing of a liquid-fuel rocket engine comprising a combustion chamber; a nozzle, consisting of a subsonic and a supersonic sections with an external structural envelope and an internal fire wall having an external ribbed surface; and a regenerative cooling passage formed between said structural envelope and said fire wall, the former being made from steel or a nickel alloy, and the latter being made from copper or a copper alloy (xe2x80x9cLiquid-fuel Rocket Engine Design and Engineeringxe2x80x9d ed. Prof. G. G. Gakhun et al., M, 1989, pp 101-111, FIG. 6.1).
In this design the internal surface of a steel structural envelope of the combustion chamber has a protective coating and the ribs of a bronze internal shell of the chamber are electroplated.
However, the known design does not always provide the required extension of the LRE chamber service life and not infrequently calls for additional measures to improve the combustion chamber wall thermal stability.
It is an object of the present invention to eliminate the aforementioned disadvantages by providing a more durable casing of the high-thrust oxygen-kerosene LRE combustion chamber.
The technical advantage resulting from the accomplishment of this object consists in the extension of the service life of the combustion chamber casing and, consequently, the combustion chamber itself and the liquid-fuel rocket engine as a whole owing to the enhancement of the thermal stability of the internal fire wall in the LRE combustion chamber casing, particularly when operating the engine on the oxygen-kerosene bipropellant. The aforementioned coating applied in the region of the nozzle throat improves the thermal stability of the fire wall in this critical area.
In accordance with the object of the invention, the LRE combustion chamber casing which comprises a combustion chamber; a nozzle, consisting of a subsonic and a supersonic sections with an external structural envelope and an internal fire wall arranged inside said structural envelope and made from copper or a copper alloy; and a regenerative cooling passage formed between said structural envelope and said internal fire wall, is characterized in that the inner surface of said internal fire wall is provided with a metal coating consisting of two layers and arranged between the subsonic and supersonic sections of the nozzle in the region of its throat over a length of not less than 0.3 diameter of the nozzle throat in the longitudinal direction, the first layer of said coating being of nickel 50 xcexcm to 1000 xcexcm thick, and the second layer of said coating located on the nickel layer being of chromium 10 xcexcm to 500 xcexcm thick.
The combustion chamber may be provided with an internal nickel coating ranging in thickness from 50 xcexcm to 1000 xcexcm.
The external structural envelope may be made from steel or a nickel alloy.
The internal fire wall of the casing can also be provided with the aforementioned stratified coating over the entire length of the wall, the first layer being of nickel, and the second layer, of chrome.
The disclosed combustion chamber casing can also be used for operation on other chemically active components of rocket engine fuel, such as hydrogen, fluorine, nitric acid, asymmetric dimethylhydrazine and other products widely used in rocket engineering.
One of the embodiments of the present invention features a nickel coating 50 xcexcm to 1000 xcexcm thick on a part of a fire wall in the combustion chamber on the side of the fire cavity, the rest of the copper or copper alloy casing wall retaining a stratified coating at least in the region of the nozzle throat over a length of not less than 0.3 throat diameter in the longitudinal direction, the first layer of said stratified coating being nickel 50 xcexcm to 1000 xcexcm thick, and the second layer of said stratified coating being chrome 10 xcexcm to 500 xcexcm thick.
This particular embodiment of the LRE combustion chamber casing is cheaper and easier to make than the casing under consideration wherein the entire fire wall of the combustion chamber has a stratified coating consisting of a nickel and a chrome layers, as indicated above.
Another embodiment of the present invention represents a different design of the combustion chamber casing portion in the supersonic section of the nozzle on the exhaust side. Unlike the previous embodiment, which provides for a steel or nickel alloy structural envelope and a copper or copper alloy internal fire wall with a stratified metal coating and a ribbed outer surface, this embodiment features a steel or nickel alloy portion of the internal fire wall without any coating on the side of the fire cavity. The supersonic section of the combustion chamber casing nozzle on the exhaust side may also be made in the form of a heat resistant metal shell serving simultaneously as an internal fire wall. It can also be manufactured from a heat-resistant nonmetal material. In both cases there is no need to apply coatings on the exhaust portion of the supersonic nozzle on the side of the fire cavity.
Yet another advantage of the latter embodiment resides in a reduction of specific amount of metal per structure of the combustion chamber casing and, consequently, in a decrease of production costs.
A fuller understanding of the aforesaid advantages and the nature of the present invention will be obtained from the following detailed description of its preferred embodiments with reference to the accompanying drawings.